Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

786
FXUS63 KLOT 110148 AAA
AFDLOT

Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
848 PM CDT Wed Jun 10 2026

.KEY MESSAGES...

- Another round of strong to severe thunderstorms is expected
  this evening. Damaging wind gusts and flash flooding are the
  biggest concerns with these storms.

- More severe weather is expected Thursday afternoon and
  evening. Damaging winds, large hail, and tornadoes will all be
  possible.

- Thursday will be another hot day with highs in the 80s and
  lower 90s and afternoon heat indices into the mid 90s.

- Friday and Saturday will be dry and noticeably cooler. A
  generally cool and at times wet pattern will develop next
  week.

&&

.MESOSCALE...
Issued at 821 PM CDT Wed Jun 10 2026

While we have had decent instability recoveries upstream of the
area, the harsh environment across northeast Illinois has now
shown its hand in a significant decaying trend in the depth of
storm cores and strength of the winds speeds. Running a quick
loop of the radar shows the southeastward surging higher
reflectivity echoes which are steering into a slightly less
worked over environment south of the I-80 and more so south of
highway 24 corridor. A notable decrease in lightning trends
suggests the severe threat is significantly diminished.

This line of storms has had some longer staying power than
expected earlier, with recent wind gusts to 40 to 45 mph in
Morris given a bit more appreciable low level shear, with gusts
to 35 mph or so as far north as the I-88 corridor. There is
also bit better instability south of a Streator to Kankakee to
Rensselaer line. Therefore a severe thunderstorm watch for
isolated damaging wind gusts is in effect until late evening
mainly south of I-80. We will continue to assess this threat
through the evening hours as additional cells develop ahead of
the main line as to how far north the severe threat will be.

These storms continue to dump decent rain with an increasing low
level jet and storms laying out more east to west, a flooding
threat does continue as these storms fall over somewhat
saturated ground from recent rains, which may be the more
immediate concern in the near term.

KMD

&&

.DISCUSSION...
Issued at 250 PM CDT Wed Jun 10 2026

Through Tonight...

Early this afternoon, we find a wave of strong to severe
thunderstorms lifting northeast through north-central IL, now
approaching the Fox Valley as of 230 PM. These storms are the
result of a shortwave impulse pushing northeast through
northwestern IL. We are safely uncapped and these storms are
certainly surface- based and tapping into over 3,000 Joules of
SBCAPE. However, the big lack of shear with rapidly growing
updrafts have kept storms from being able to achieve much
organization. The strongest storms thus far have been tracking
closer to the wave itself while additional storms are going up
farther south. This prompted an initial Severe Thunderstorm
Watch to be issued across our northwest counties. This trend is
expected to continue with most recent CAM guidance resolving the
strongest convection through the rest of the afternoon favoring
areas north of I-80 and especially up toward WI. A new
downstream Watch is in the process of being drawn up as of this
writing. These storms have a history of producing 70+ mph just
west of our CWA and likely at least some small hail. Damaging
winds will continue to be the biggest concern with storms this
afternoon with locally destructive gusts possible. The tornado
threat appears minimal this afternoon, especially if we`re
hardly seeing any signs of subtle rotation out to our west right
now where/when the threat would conceptually be "maximized"
around the CWA. Hail, likely sub-severe and non-damaging, is
also a concern with these storms.

The storms have also been producing torrential rainfall with
observations and MRMS reading over an inch in an hour in parts
of north-central and northwest IL and instantaneous rates up to
3 to 4 inches per hour. If this were to continue, this could
certainly lead to localized flooding or ponding issues,
particularly in low-lying and more developed areas. Given that
storms are moving along at around 45 mph and the heaviest rain
is only lasting a handful of minutes over a given area,
widespread flooding issues are not anticipated. This could
change if additional upstream storms develop or convection
clings onto any sort of outflow boundaries meandering about, but
there`s no sign of this occurring as of yet.

Looking to our next round, a second shortwave impulse/vort lobe
will eject east across central IL this evening. It`s expected
to fire up additional storms across western portions of MO and
IA later this afternoon and carry them east across the area
during the evening along with the help of a modest low level jet
nose pointing into west-central IL. Latest guidance is honing
in on an eastward- propagating bowing MCS for a storm mode.
Still some varying intensities among models with the strongest
storms generally favored near and south of I-80 along the track
of the wave where forcing will be strongest. Nonetheless, areas
farther north are still very much in play for additional severe
storms tonight. Most CAMs also depict a general weakening of
the line with eastward extent across our area, which would make
sense as storms become further removed from the better shear and
kinematic forcing. The severe threat should exit the area to
the east around midnight with some showers or non-severe storms
possibly lingering behind for a couple of hours. Biggest concern
with this second round will again be damaging wind gusts. High
res camps favor these storms leaving behind a stalled outflow
boundary which could possibly retrigger some additional showers
or storms into the night, but this is not anticipated. Flash
flooding appears to again be more of a localized concern, though
it`s worth mentioning that areas south of I-80 will be
generally more sensitive to heavy rainfall given recent rain.


Thursday and Thursday Night...

An especially sharp shortwave impulse will quickly spin up east
of the Colorado Rockies this evening and propagate
northeastward through the night reaching our vicinity by
tomorrow afternoon. The surface reflection will be a deepening
center of low pressure. A frontal boundary stalling across
northern IL or southern WI tonight will cling onto to this new
circulation serving as its warm front. The advancement of the
low will push the front farther north into Wisconsin reinforcing
the high theta-e airmass for the day. We may have to keep an
eye out for a sneaky morning setup in which showers and
thunderstorms may attempt to develop along and overtop any
stalled outflow/pseudo-front from tonight`s storms, particularly
south of I-80. The NAM is an outlier in showing some spotty
light QPF while other camps remain dry owing to a lack of any
additional forcing. While the potential appears low, felt it was
still worth mentioning given that training and flash flooding
would be a concern if storms do decide to go. Treated this with
unmentionable PoPs (<15%) in the forecast. During the afternoon
prior to the arrival of storms, temperatures are forecast to get
back into the 80s and lower 90s with heat indices well into the
90s.

Guidance is in solid agreement on a strongly forced line of
convection moving east across the area along the storm`s cold
front. An initial, pre-frontal push of some severe storms will
be possible as well in the late morning and early afternoon
ahead of the front. Solutions which track the low center nearer
to northern IL are most excited about this initial push
impacting our area, and favor northwestern portions of the CWA.
The primary push of storms is slated for the mid-afternoon
through mid-evening. The storm`s warm sector will feature 3,000
to 4,000+ Joules of uncapped SBCAPE and over 50kt of effective
shear. An all hazards severe event appears to be in the cards
with damaging to destructive winds, hail, and tornadoes all
possible. Given a great deal of low level instability, prime
environment for deep, persistent updrafts, and long, curved low
level hodographs ahead of the front, a few strong (EF2+)
tornadoes are on the table. With PWATs hanging out above 1.5"
tomorrow, more torrential downpours and flash flooding will be
possible. Given the progressive nature of the storms among other
factors, widespread impactful flooding does not look likely,
but rather on a more localized basis. Any areas that receive a
good amount of rain or any flooding today and tonight will be
especially vulnerable to flooding issues tomorrow. SPC has
maintained their level 3 of 5 Enhanced Risk over the area.

Doom


Friday onward:

A break in the hot and stormy pattern is expected Friday and
Saturday as a surface high pressure system works through the
region. Highs on Friday should top off in the upper 70s (locally
80), and lows Friday night should fall into the lower 60s.
Ensemble guidance than depicts the development of expansive
troughing across the northern United States next week. While the
main reservoir of hot and humid air would get shunted well
south of our area, a parade of shortwaves may lead to periodic
opportunities for showers and thunderstorms across our region
through next week.

Borchardt

&&

.AVIATION /00Z TAFS THROUGH 06Z FRIDAY/...
Issued at 642 PM CDT Wed Jun 10 2026

Aviation forecast concerns for the 00Z TAFs:

- Another round of TSRA expected this evening, though likely not
  as strong as storms earlier this afternoon especially for CHI
  metro.

- Chance (~30 percent) of late morning/midday storms along the
  IL/WI border (RFD mainly), then strong/severe storms likely
  for all sites Thursday late afternoon/evening.

- Breezy south winds ahead of late Thursday storms, with gusts
  around 30 kt possible.

Initial strong/severe squall line which impacted the terminals
this afternoon has moved east of the area. Another line of TSRA
has developed across eastern IA, however, and was approaching
the Mississippi River at issuance time. Large footprint of cool,
stable outflow air from earlier storms was in place across much
of northern IL, though a developing low-level jet and steep
mid-level lapse rates will likely allow current IA storms to
continue to propagate eastward across the terminals this
evening. These storms may tend to be slightly more elevated
(storm inflow source from above the more stable boundary layer),
which may decrease surface wind gust potential somewhat
especially with eastward extent - though confidence in this is
rather low. Have included TEMPO mentions at all sites for these
storms, starting at 01Z for RFD, 02Z for most of the Chicago
sites. Storms and a period of trailing stratiform rain should
exit to the east by late evening/midnight.

Moist low-level air mass will linger overnight (and into
Thursday), and may support development of patchy MVFR ceilings
into Thursday morning, though confidence on extent/location is
low at this time. On Thursday, surface low pressure is forecast
to lift northeast across IA into WI through the
afternoon/evening hours, supporting strengthening south winds
across the area. Wind gusts around 30 kts (potentially higher)
appear likely during the afternoon hours.

There remains some model support for another cluster of
thunderstorms to track across northwest IL into southern WI late
Thursday morning/midday. Have maintained a PROB30 for TS at RFD
for this, with lower confidence of it affecting the Chicago
metro sites. Higher confidence persists for another line of
strong/severe thunderstorms ahead of a cold front late Thursday
afternoon/evening.

Ratzer

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Flood Watch until 4 AM CDT Thursday for ILZ010-ILZ011-ILZ012-
     ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-
     ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.

IN...Flood Watch until 4 AM CDT /5 AM EDT/ Thursday for INZ001-
     INZ002-INZ010-INZ011-INZ019.

LM...Small Craft Advisory until 9 PM CDT this evening for the IL
     and IN nearshore waters.

&&

$$

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